Generally, in electric rooms of buildings, factories, apartment complexes, or the like, distribution boards are installed to receive high-voltage or extra high-voltage electricity and to distribute electricity to each customer load. The distribution board is divided into an extra high-voltage panel, a transformer panel, and a low-voltage panel according to a current carrying path and voltage of a power system; and the extra high-voltage panel is generally composed of a high-tension power board (LBS), a voltage current transformer for metering (MOF), a voltage transformer for metering (PT), a circuit breaker (VCB), and the like.
The distribution board includes various types of electrical equipment, such as Load Break Switch (LBS), Lightening Arrester (LA), Power Fuse (PF), Metering Out Fit (MOF), Vacuum Circuit Breaker (VCB), and the like; and a bus bar electrically connected with the electrical equipment to input and output electricity supplied from an external source, in which a high-voltage current flows between the electric equipment and the bus bar.
In the case where there is a problem with the distribution board, in order to check or repair the bus bar and each piece of electrical equipment, an operator opens the door of the distribution board, and performs the repair work at a position close to each piece of electric equipment or the bus bar. During such repair work, accidents frequently occur in which the operator gets high-voltage electric shock because of carelessness.
In order to prevent such electric shock accidents, an operator, before checking and repairing the distribution board, is required to completely block electricity supplied to the distribution board by opening various load breakers of the distribution board; to perform voltage detection to check whether a bus bar or electrical equipment is in live state and whether there is a charged electric charge; and to perform a discharging operation to completely discharge charged electric charge. By doing these power cut-off operations, which are a series of safe work practices, electric shock may be prevented even if the operator comes into contact with a bus bar or electrical equipment to check or repair the distribution board.
Upon completing the power cut-off operations, the operator further performs short-circuiting and grounding in the distribution board, performs an operation to prevent input of a circuit breaker (indicating supply of electricity), and then checks and repairs the distribution board. Upon completing the checking and repairing operation, power is provided to electric equipment in reverse order to the aforementioned order of operations, so that the distribution board may operate.
During the power cut-off operations, when a circuit breaker is cut off or a discharging operation is performed, there may be a case where a large arc is generated due to a live wire, indicating a state where electricity flows to electrical equipment, and the charged electric charge. For this reason, in order to prevent electric shock, an operation to prevent input of a circuit breaker or a discharging operation should be performed with a sufficient safety distance from a bus bar or electrical equipment.
However, since blackout accidents caused by the failure in the distribution board have significant effects and results in serious problems, an operator may impatiently hurry to fast check and repair the failure, and may ignore safety regulations, without performing power cut-off operations, to immediately check the distribution board, which leads to frequent electric shock accidents.
In order to prevent such electric shock accidents, there are general methods including: giving a warning to an operator when the operator violates regulations of the power cut-off operations or when the operator approaches too close to electrical equipment or a bus bar without performing safety procedures; cutting off a circuit breaker (which indicates shutting off electricity); or further providing an auxiliary door at a position corresponding to an inner portion of the door of a distribution board to prevent access to electrical equipment or a bus bar.
However, the general methods have a drawback in that the methods, which are merely about calling an operator's attention, may not protect the operator by forcibly preventing the operator from ignoring safety regulations and from performing operations carelessly.
Further, in the case where an operator works in a large distribution board, the general methods have no function to check the operator, such that there may be a case where other operators, without knowing that the operator is working in the distribution board, may input a circuit breaker for normal operation of the distribution board, which may lead to electric shock accidents.